CN113543989B

CN113543989B - Pneumatic tire

Info

Publication number: CN113543989B
Application number: CN202080019471.0A
Authority: CN
Inventors: 安藤宽太
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2019-10-08
Filing date: 2020-09-15
Publication date: 2023-10-20
Anticipated expiration: 2040-09-15
Also published as: JP2021059257A; CN113543989A; EP4043240A4; WO2021070581A1; JP6969596B2; EP4043240A1; US20230074596A1

Abstract

A pneumatic tire capable of securing fitting with a rim, improving productivity, and improving recycling of materials. The pair of bead portions (5) are each composed of an annular bead core (10) made of a thermoplastic resin and a bead core cover (20) made of a thermoplastic resin.

Description

Pneumatic tire

Technical Field

The present application relates to a pneumatic tire having a bead portion with a bead core formed of a thermoplastic resin.

Background

In the conventional pneumatic tire, the basic characteristics of the tire are ensured by using a vulcanized rubber and a cord material such as an organic fiber or a steel fiber. However, the vulcanized rubber has a problem that recycling of materials is difficult. In addition, the use of a cord material, particularly a carcass cord, has a problem of complicating a manufacturing process and increasing manufacturing costs.

Accordingly, patent document 1 below proposes a carcass-less (carpassless) tire in which a tire frame member is formed of a thermoplastic resin. The tire frame member has: a pair of bead portions, a pair of sidewall portions extending from the pair of bead portions, and a crown portion connecting the pair of sidewall portions.

[ Prior Art literature ]

[ patent literature ]

Patent document 1: japanese patent No. 6138695

Disclosure of Invention

[ problem to be solved by the application ]

However, in the tire proposed above, as the bead core, a wound body of a bead cord using metal fibers such as steel fibers and organic fibers such as aromatic polyamide fibers is used.

Therefore, in the case of manufacturing a tire, a step of winding the bead cord and forming the bead core is required in advance, and there is a problem that the production efficiency is lowered. Further, since the bead cord uses a metal fiber or the like, there is a problem that the recyclability of the material cannot be sufficiently improved.

The application provides a pneumatic tire, which is based on at least a bead part with a bead core composed of thermoplastic resin, can ensure the joggability with a rim, and can improve the production efficiency and the recycling property of materials.

[ means for solving the problems ]

The present application relates to a pneumatic tire having a pair of bead portions fitted to a rim,

the pair of bead portions are each constituted by an annular bead core formed of a thermoplastic resin and a bead core cover formed of a thermoplastic resin.

In the pneumatic tire of the present application, preferably, the pneumatic tire includes a pair of side wall portions extending from the pair of bead portions in the tire radial direction, respectively, and a bottom tread portion connecting the pair of side wall portions,

the pair of sidewall portions and the bottom tread portion are formed of a thermoplastic resin that is the same as or different from the thermoplastic resin of the bead core covering portion.

In the pneumatic tire of the present application, it is preferable that a tread land member is provided on the outer side in the tire radial direction of the bottom tread portion,

the tread contact member is formed of vulcanized rubber or thermoplastic resin.

In the pneumatic tire of the present application, preferably, the thermoplastic resin of the bead core has a tensile elastic modulus of 1000MPa or more.

In the pneumatic tire of the present application, preferably, the thermoplastic resin of the bead core has a tensile elastic modulus greater than that of the thermoplastic resin of the bead core covering portion.

In the pneumatic tire of the present application, preferably, the thermoplastic resin of the bead core covering portion has a tensile elastic modulus of 30 to 200MPa.

In the pneumatic tire of the present application, preferably, the bead core contains a fibrous filler in the thermoplastic resin.

In the pneumatic tire of the present application, preferably, the filler is oriented in the tire circumferential direction.

[ Effect of the application ]

In the pneumatic tire of the present application, each of the pair of bead portions is composed of an annular bead core made of a thermoplastic resin and a bead core cover made of a thermoplastic resin.

Therefore, at least in the bead portion, for example, by injecting 2 kinds of thermoplastic resins into a cavity (cavity) and performing composite molding, the bead core and the bead core covering portion can be integrally formed at one time.

That is, a separate process for forming the bead core is not required, and the production efficiency can be improved. In addition, since the thermoplastic resin can be used for the bead core, the recyclability of the material can be further improved. Further, the adhesion between the bead core and the bead core covering portion increases, and can also contribute to improvement of bead durability.

Drawings

FIG. 1 shows a cross-sectional view of one embodiment of a pneumatic tire of the present application.

Fig. 2 is an enlarged sectional view of the bead portion.

Fig. 3 shows an enlarged cross-sectional view of the tread reinforcing member.

FIG. 4 shows a cross-sectional view of other examples of tread reinforcing members.

Fig. 5 (a) to (c) are conceptual views showing a method of manufacturing a pneumatic tire.

[ reference numerals ]

1. Pneumatic tire

3. Tread ground contact member

5. Bead portion

6. Sidewall portion

7. Undertread portion

10. Tire bead core

20. Bead core covering part

R rim

Detailed Description

Embodiments of the present application are described in detail below.

As shown in fig. 1, a pneumatic tire 1 (hereinafter, may be simply referred to as a tire 1) of the present embodiment includes a pair of bead portions 5, and each of the pair of bead portions 5 includes an annular bead core 10 made of a thermoplastic resin and a bead core cover 20 made of a thermoplastic resin.

In this example, the pneumatic tire 1 is shown as a passenger tire. However, the present application is not limited thereto, and the present application can be applied to various types of tires for automatic two-wheeled vehicles, light-duty vehicles, large-size vehicles, and the like.

Specifically, the tire 1 has at least: an annular tire frame member 2 including a pair of bead portions 5, and a tread ground-contacting member 3.

The tire frame member 2 includes: the pair of bead portions 5, a pair of sidewall portions 6 extending outward in the tire radial direction from the pair of bead portions 5, and an under tread portion 7 connecting the pair of sidewall portions 6.

The bead portion 5 is a portion fitted to the rim R at the time of rim assembly. The sidewall 6 is a portion constituting a side portion of the tire 1, and extends outward in the tire radial direction while being curved in a convex arc shape toward the tire axial direction outer side. The under tread portion 7 is a portion supporting the tread ground-contacting member 3, and connects between the tire radial outer ends of the side wall portions 6.

As described above, the bead portion 5 is constituted by the annular bead core 10 formed of the thermoplastic resin, and the bead core cover 20 formed of the thermoplastic resin.

Here, as the thermoplastic resin of the bead core 10, one having a tensile elastic modulus E5 greater than a tensile elastic modulus E3 of the thermoplastic resin of the bead core covering portion 20 may be used. In particular, as the thermoplastic resin for the bead core 10, a thermoplastic resin having a tensile elastic modulus E5 of 1000MPa or more, more preferably 5000MPa or more is preferably used in order to bring the fitting force with the rim R to a level close to that of a bead core made of a conventional steel cord. In addition, when the tensile elastic modulus E5 exceeds 30000MPa, the rim assembly performance tends to be impaired. In the bead core 10, the tensile strength of the thermoplastic resin is also preferably 200MPa or more. The tensile elastic modulus and the tensile strength are values measured according to the test method described in "method for determining plastic-stretching characteristics" of JIS K7161.

Preferably, fibrous filler is contained in the thermoplastic resin of the bead core 10. At this time, it is further preferable to orient the filler in the tire circumferential direction. By orienting the filler in the tire circumferential direction, a strong band effect (a "band effect") can be exerted on the tire circumferential direction, and the fitting force with the rim can be improved. On the other hand, since deformation with respect to the tire radial direction can be allowed, an effect of easy rim assembly can be obtained. Examples of suitable fillers include carbon fibers, glass fibers, aramid fibers, cellulose Nanofibers (CNF), cellulose Nanocrystals (CNC), and the like, which may be used alone or in combination.

In the thermoplastic resin of the bead core covering portion 20, the tensile elastic modulus E3 is preferably in the range of 30 to 200MPa. By setting the tensile elastic modulus E3 to 30MPa or more, the lateral rigidity of the tire can be ensured, and excellent steering stability can be exhibited. However, when the tensile elastic modulus E3 exceeds 200MPa, the bead portion 5 becomes excessively hard, and the fitting property with the rim R tends to be lowered.

In the tire 1, the side wall portion 6 and the under tread portion 7 are also formed of thermoplastic resin. In this case, the sidewall portion 6, the under tread portion 7, and the bead core cover 20 may be formed of the same thermoplastic resin or may be formed of different thermoplastic resins. It is preferably formed of the same thermoplastic resin from the viewpoint of productivity, but it is preferably formed of a different thermoplastic resin from the viewpoint of running performance.

When formed of different thermoplastic resins, it is more preferable to use, as the thermoplastic resins of the sidewall portion 6 and the under tread portion 7, a thermoplastic resin having a tensile elastic modulus E2 smaller than a tensile elastic modulus E3 of the thermoplastic resin of the bead core covering portion 20. Thus, both steering stability and riding comfort can be achieved.

As shown in fig. 2, from the viewpoint of improving the bonding strength, it is preferable that the boundary surface K between the thermoplastic resin of the bead core covering portion 20 and the thermoplastic resin of the sidewall portion 6 be inclined with respect to the tire axial line. It is particularly preferable that the intersection point Po between the outer surface of the tire frame member 2 and the boundary surface K is located further inward in the tire radial direction than the intersection point Pi between the inner surface of the tire frame member 2 and the boundary surface K. This reduces the exposed area of the outer surface of the bead core covering portion 20, and thus helps to suppress damage such as cracking accompanying deformation of the tire.

Preferably, the height hb in the tire radial direction between the intersection point Po and the bead Base Line (BL) is in the range of 1.0 to 3.0 times the rim edge height hf. When the amount is less than 1.0 times, it is difficult to sufficiently improve the steering stability. Conversely, if the ratio exceeds 3.0 times, not only the effect of suppressing damage such as cracking is reduced, but also riding comfort is adversely affected. The rim edge height hf is defined as the height between the top of the rim edge Rf and the bead base line BL in the tire radial direction.

As shown in fig. 1, the tread ground-contacting member 3 is disposed radially outward of the undertread portion 7. In this example, a case is shown in which the tread reinforcing member 4 is further arranged between the tread ground-contacting member 3 and the under tread portion 7.

The tread ground contact member 3 is a portion for being grounded to a road surface, and tread grooves 9 for improving wet performance are formed in various patterns on the ground contact surface 3S. The tread ground-contacting member 3 may be formed of vulcanized rubber or thermoplastic resin. However, from the viewpoint of improving the recyclability of the material, it is preferable that the tread ground-contacting member 3 is also formed of a thermoplastic resin.

In the case of using the thermoplastic resin for the tread land member 3, from the viewpoint of improving the following property to the road surface and improving the grip, it is preferable that the tensile elastic modulus E1 of the thermoplastic resin for the tread land member 3 is smaller than the tensile elastic modulus E2 of the thermoplastic resin for the sidewall portion 6 and the under tread portion 7.

However, when the thermoplastic resin having E1< E2 is used for the tread land member 3, the tread rigidity may be reduced, and the stability of the ground contact shape may be lowered, which may reduce the steering stability. Therefore, in the present embodiment, the tread reinforcing member 4 and the tread portion 7 are provided, so that the stability of the tire shape (particularly, the ground contact shape) can be achieved. Thus, even when the thermoplastic resin having E1< E2 is used for the tread ground-contacting member 3, excellent running performance can be exhibited.

As shown in fig. 3, in this example, the tread reinforcing member 4 is formed of a cord reinforcing layer 12 in which reinforcing cords 11 are arranged. Specifically, the cord reinforcement layer 12 is formed of 1 or more (e.g., 2) reinforcing cords 14. The reinforcing cord 14 of this example is in the following sheet form: a sheet-like structure formed by covering an array of reinforcing cords 11 arranged at an angle of, for example, 10 to 45 degrees with a rubberizing (taping) material 13 formed of rubber or a thermoplastic resin with respect to the tire circumferential direction. When the reinforcing cord 14 is provided in a plurality of pieces, the inclination direction of the reinforcing cords 11 between the cords is preferably different. The reinforcing cord 14 may be an array of reinforcing cords 11 spirally wound in the tire circumferential direction covered with the rubberizing material 13.

As the rubberizing material 13 of the reinforcing cord 14, a thermoplastic resin is suitably used from the viewpoint of adhesion to the tread ground-contacting member 3 and the under tread portion 7.

As shown in fig. 4, the tread reinforcing member 4 may be a resin reinforcing layer 15 formed of a thermoplastic resin. In the case of the resin reinforcing layer 15, it is preferable to include a fibrous filler in the thermoplastic resin, and it is further preferable to orient the filler in the tire circumferential direction.

Examples of suitable fillers include carbon fibers, glass fibers, aramid fibers, cellulose Nanofibers (CNF), cellulose Nanocrystals (CNC), and the like, which may be used alone or in combination.

In the present application, "thermoplastic resin" includes thermoplastic elastomers. The "thermoplastic resin" is a polymer compound that softens with an increase in temperature, flows, and becomes a relatively hard and strong state after cooling. "thermoplastic elastomer" has the following characteristics: the material softens with an increase in temperature, flows, cools, becomes harder and stronger, and has rubber-like elasticity.

In view of the elasticity required for running, the formability during manufacturing, and the like, a thermoplastic elastomer is suitably used for the tread ground-contacting member 3, the undertread portion 7, the sidewall portion 6, and the bead core covering portion 20, and a thermoplastic resin having no rubber-like elasticity is suitably used for the bead core 10.

Examples of the thermoplastic elastomer include polyamide-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polystyrene-based thermoplastic elastomer, and polyolefin-based thermoplastic elastomer, which may be used alone or in combination.

In the present application, different thermoplastic resins mean that the compositions of the thermoplastic resins are different from each other, and "composition is different" means that the components constituting the thermoplastic resins are the same and their contents are different in addition to the components themselves (including additives).

Next, an example of a method for manufacturing the tire 1 according to the embodiment is shown. As conceptually shown in fig. 5, the manufacturing method of this example includes:

a step S1 of forming a 1 st tire base 1A by integrating the bottom tread portion 7, the tread reinforcing member 4 and the tread ground-contacting member 3,

a step S2 of forming a 2 nd tire base 1B obtained by integrating the sidewall 6, the bead core cover 20 and the bead core 10,

step S3 of joining the 1 st tire base 1A and the 2 nd tire base 1B to form the tire 1.

In step S1, when the tread reinforcing member 4 is the cord reinforcing layer 12, after the cord reinforcing layer 12 is formed in advance, a thermoplastic resin for the tread reinforcing member and a thermoplastic resin for the under tread portion are injected into a cavity (cavity) in which the cord reinforcing layer 12 is provided, and composite molding is performed, whereby the 1 st tire base 1A is formed. When the tread reinforcing member 4 is the resin reinforcing layer 15, the thermoplastic resin for the tread reinforcing member, the thermoplastic resin for the under tread portion, and the thermoplastic resin for the resin reinforcing layer are injected into the cavity, and the composite molding is performed, thereby forming the 1 st tire base 1A.

In step S2, a thermoplastic resin for the bead core cover, and a thermoplastic resin for the sidewall portion are injected into the cavity, and subjected to composite molding, thereby forming the 2 nd tire base 1B.

In step S3, the 1 st tire base 1A and the 2 nd tire base 1B are joined by heat fusion or using an adhesive. As the adhesive, for example, aronaalpha EXTRA 2000 (registered trademark) manufactured by Toyama Synthesis Co., ltd, LOCTITE 401J (registered trademark) manufactured by Henkel Japan Co., ltd, or the like can be suitably used.

The present application is not limited to the illustrated embodiments, but may be modified and implemented in various ways.

Examples

In order to confirm the effect of the present application, tires (195/65R 15) for passenger vehicles having the structure shown in FIG. 1 were produced according to the specifications of Table 1. Then, the rim assembling property, fitting property (fitting force of the bead portion to the rim) and productivity of each of the test tires were tested.

In comparative example 1, the structure was substantially the same as that of the example except that the bead core was a core formed of steel cords. In examples 1 to 6, a filler made of glass fiber was added to the bead core.

< rim Assembly Property >

The presence or absence of damage such as cracking of the bead portion when the tire is assembled with the automatic rim assembling machine rim is visually checked. Based on these inspection results, rim assemblability was evaluated on a 10-class scale. The larger the index value, the more excellent the rim assemblability.

< chimerism >

The fitting force (unit: kN) of Huffman (Hofmann) was measured using a bead portion expansion force tester manufactured by Huffman company. The measurement results are shown as an index of 100 in comparative example 1. The larger the number, the larger the engagement force, the better.

< productivity >

The productivity of the tire is shown by an index of 10 in comparative example 1. The larger the number, the more excellent the productivity.

TABLE 1

The resin materials used in table 1 are shown in table 2.

TABLE 2

As shown in table 1, it was confirmed that the examples can provide tires with necessary chimerism while improving productivity. And it is understood that the bead core is formed of a thermoplastic resin, thereby also contributing to improvement in material recycling.

Claims

1. A pneumatic tire, characterized in that,

the pneumatic tire has a pair of bead portions fitted to a rim,

A pair of side wall parts extending from the pair of bead parts along the radial direction of the tire,

A bottom tread portion connecting the pair of sidewall portions,

A tread ground contact member provided on the outer side in the tire radial direction of the bottom tread portion, the pair of bead portions each being constituted by an annular bead core formed of a thermoplastic resin and a bead core cover formed of a thermoplastic resin,

the pair of sidewall portions and the bottom tread portion are formed of the same thermoplastic resin as that of the bead core covering portion,

the thermoplastic resin of the bead core has a tensile elastic modulus of 1000MPa or more,

the thermoplastic resin of the bead core covering portion has a tensile elastic modulus of 30 to 200MPa,

the thermoplastic resin of the bead core contains fibrous filler therein,

the fibrous filler comprises glass fibers.

2. The pneumatic tire of claim 1, wherein the tread ground-contacting member is formed of vulcanized rubber.

3. The pneumatic tire according to claim 1, wherein the tread ground-contacting member is formed of a thermoplastic resin having a tensile elastic modulus smaller than that of the thermoplastic resin of the sidewall portion and the bottom tread portion.

4. A pneumatic tire according to any one of claims 1 to 3, wherein the filler is oriented in a tire circumferential direction.